Respiration 3 Flashcards
What controls ventilation rate?
Blood levels of CO2
directly linked to metabolic rate
Name 4 neuron groups of the respiratory centre and their roles?
dorsal respiratory group, dorsal medulla, mainly causes inspiration;
ventral respiratory group, ventrolateral medulla, modifies expiration and inspiration;
pneumotaxic center, dorsally in the superior pons, mainly controls rate and depth of breathing;
apneustic centre;
Where is the respiratory centre located ?
Neurons are bilateral in the medulla oblongata and pons
Link basics rhythmic breathing and inspiratory neuronal activity
During inspiration, the activity of inspiratory neurons increase steadily
By the end the activity ends abruptly and expiration occurs by elastic recoil of lungs
What regulates the pneumatic centre?
Vagal input - stretching of lung
Pneumotaxic Centre
What are the two roles of the pneumotaxic centre?
Limits length of inspriation
Increases the rate of breathing
How is the ventral respiratory neuron group useful during exercise?
Stimulation of some neurons in the ventral group causes stronger inspiration, whereas stimulation of others causes forced expiration.
The ventral respiratory area contributes to both inspiration and expiration. Important for sending signals to the abdominal muscles during very heavy exercise
Respiratory centres have what 2 things in common?
Basic rhythmic activity (DRC) Regulatory activity (Pneumtaxic and Apneustic centres)
What regulates the respiratory centre activities
Central (Medullary) Chemoreceptors
Cortical factors
Local reflexes- Baroreceptors, Peripheral chemoreceptors,
What is the most important control to the respiratory centre activities?
What triggers it?
Central chemoreceptors
pH of the cerebrospinal fluid
CO2 potent but indirect effect
What is Herring-Breuer Reflex?
Stretch receptors in chest wall and in the bronchi and bronchioles (over smooth muscle) send impulses to the brain to terminate inspiration.
What is the roles of the Herring-Brueuer Reflex?
Protective reflex prevent over expansion of the lungs
Coordinates the apneustic + pneumotaxic centre
State the difference between the roles of the Herring -Breuer reflex in adults and in infants
Infants- regulates basic rhythm of breathing and preventing over inflation of the lungs
Adults- only important when tidal vol large -during exercise
When do peripheral chemoreceptors play a role?
When blood O2 falls too low as it has a large effect on respiration.
Only when o2 is low
How do oxygen sensors work?
Carotid body chemoreceptor cells respond to hypoxia (low oxygen) by inhibiting potassium channels, leads to depolarization and the activation of voltage-dependent calcium channels. Calcium influx results in exocytosis of the neurotransmitter dopamine that increase the activity of the afferent chemosensory fibres.
What is the effect of CO on [o2] in the blood?
[O2] decreases but pO2 not reduced
ie amount in solution in arterial blood is the same, BUT very little bound to Hb)
What causes Histotoxic-hypoxia?
Inhibition of tissue oxidative processes by poisons. e.g., Cyanide - combines with cytochrome oxidase preventing O2 from serving as the ultimate electron acceptor
What causes Stagnant-hypoxia?
And what is its effect?
due to poor circulation
causes Shock
Congestive heart failure (or localized restriction
What causes anemic-hypoxia?
Essentially low Hb content.
Also in CO poisoning, effective Hb content is reduced by HbCO complexes.
What causes Hypoxic-Hypoxia
(pO2 of arterial blood is reduced). e.g., breathing O2 at reduced atmospheric pressures. When pO2 of inspired air falls to about 60-70 mmHg (Mont Blanc) there is risk of loss of consciousness.
At sea level when breathing in an environment with 10% or less O2.
With altitude (composition of air remains the same) but pressure changes.
